ANIMAL BEHAVIOUR 223 



haviour of higher animals. They show a ' trial-and-error ' 

 method, a selection of regulatory responses, and, for a short time at 

 least, a profiting by experience. There is experimenting below the 

 level of perceptual inference. 



Among the more complex animals there seem to be two distinct 

 modes of effective behaviour, namely, instinctive and intelligent be- 

 haviour. The former finds its finest expression in the ' little brain ' 

 types, such as ants, bees, and wasps; the latter in the 'big brain' 

 types, such as birds and mammals. Each mode has its excellencies 

 and its limitations. 



Instinctive behaviour agrees with reflex action in being dependent 

 on a hereditary nervous predisposition characteristic of the species, 

 but it is a concatenated series of correlated acts of the whole crea- 

 ture. There is a hereditary awareness of the practical significance 

 of certain things and configurations, and a hereditary impulsion 

 to a precise routine. The capacity may be improved by experience, 

 but it is to some degree independent of individual learning. It 

 is not experimental, inferential, or reflective like intelligent be- 

 haviour, and has very striking limitations. It is often linked with 

 intelligence, especially in the ' big brain ' types, such as birds. 



As regards the nature of instinct, there are three main theories 

 at present in the field, between which it is too soon to decide dog- 

 matically. (A) Some investigators rank instinctive behaviour near 

 reflex actions, as due to non-cognitive hereditary predispositions to 

 follow out a certain routine when a number of triggers are pulled. 

 (B) Others regard instinctive behaviour as quite inseparable from 

 intelligent behaviour. (C) According to others, instinct and in- 

 telligence are two radically different, though often co-operative, 

 kinds of knowing, which have evolved along divergent lines. 



Among birds and mammals, in particular, there is evidence of 

 intelligent behaviour. It implies, objectively, some 'trial-and- 

 error' experiments and profiting thereby. It implies, subjectively, 

 some perceptual inference. It is reflective as contrasted with in- 

 stinctive. 



As is well known, a secondary simplicity often comes about in the 

 individual lifetime, when what originally required attentive selection 

 and detailed control becomes habitual. But it is not known to 

 what extent, if any, the results of habituation can be entailed on 

 the offspring. It seems at present improbable that instincts can 

 arise in this way. Yet, as will be seen later on, it seems to be 

 part of the tactics of Animate Nature to economise mental activity 



